Novel solid-state imaging devices with inherent MNOS memory gate

A novel solid-state imaging device with an inherent MNOS memory gate is proposed and writing and reading characteristics are discussed. To improve the writing of the low light inputs, a bias charge in addition to the signal charge is transferred into the MNOS memory Capacitor from a photodiode. Both enhanced writing and a Wide dynamic range are obtained under the following optimum bias condition: a preset photodiode voltage of 5 V, a memory pulse voltage of 35 V amplitude, and a 1-10 µs duration. Moreover, it was found that the stored charge signal could be nondestructively read from drain output under bias light, provided the drain voltage V
D
was biased higher than the Surface potenteal φ
MG
in the depletion layer below the memory gate. If V
D
< φ
MG
, however, incoming light signals are detected regardless of shifts in the flat-band voltage optically induced during the Writing process. Finally, the reproduced images of readout and incoming light signals are demonstrated using a 5 × 5 2-D array.